Diabetic Retinopathy Features Detected with 6x6 mm OCT Angiogram Using SSADA Algorithm

Abstract

 

Purpose

 

Diabetic retinopathy (DR) is a common retinal vascular disease with classic fluorescein angiography (FA) features that are useful for treatment and classification. OCT Angiography is a dye-free alternative to FA. Using a commercially available 70kHz OCT and the split-spectrum amplitude decorrelation angiography (SSADA) algorithm, 6x6 mm images can be obtained in 3.5 seconds. We evaluated the ability of this technique to detect the angiographic features catalogued by the Early Treatment of Diabetic Retinopathy Study (ETDRS).

 

Methods

 

Four patients with DR were imaged with conventional FA and OCT angiography. The images were evaluated for the ability to detect ETDRS features and other manifestations of vasculopathy.

 

Results

 

OCT angiography detected enlargement and distortion of the foveal avascular zone, retinal capillary dropout, and pruning of arteriolar branches. Areas of capillary loss obscured by fluorescein leakage on FA were more clearly defined on OCT angiography. Some areas of focal leakage on FA that were thought to be microaneurysms were found to be small small tufts of neovascularization that extended above the inner limiting membrane.

 

Conclusions

 

OCT angiography does not show leakage, but can better delineate areas of capillary dropout and detect early retinal neovascularization. This new noninvasive angiography technology may be useful for routine surveillance of proliferative and ischemic changes in diabetic retinopathy.  

 

Figure 1 shows 6x6 mm fluorescein angiography (A) OCT angiogram (B) of a patient with diabetic retinopathy with ETDRS grid superposed showing FAZ enlargement inferotemporally and temporally between the 300 (dotted) and 500 µm circles. Flow signal detected between retinal pigment epithelium (RPE) and the internal limiting membrane (ILM) is shown in magenta and signal internal to the ILM is displayed in yellow. Magnified FA (C) shows corresponding FAZ enlargement.

 

 

Figure 2: OCT angiogram (A) and FA (B) discloses areas of capillary dropout in the temporal macula with pruning of the arterioles. In the FA, diffuse leakage obscures an area of capillary drop out seen on OCT angiography (red arrows). An arteriole with vessel wall staining and narrowing (blue arrow) in the FA is shown to be a barely visible ghost vessel on OCT angiography. Focal areas of leakage near the fovea thought to be large microaneurysms on FA were shown to be NV on OCT angiography (green arrows).